Hurricane warnings for Baja; 94L forming spiral bands

Hurricane warnings are in effect for the southern tip of Mexico's Baja Peninsula, where powerful Hurricane Jimena is expected to make landfall Tuesday night or Wednesday morning. The hurricane is in an environment with low wind shear, 5 - 10 knots, and warm Sea Surface Temperatures (SSTs), 30°C. Shear is expected to remain low, and SSTs will decline to 28°C with a corresponding decrease in total oceanic heat content between now and landfall, and these conditions should mean that Jimena will be a Category 3 or 4 hurricane at landfall. Outer rain-bands of the hurricane will be appearing on Los Cabos radar soon, though the Mexican Weather Service web site has been hard to reach today. The computer models are split, with one camp calling for a landfall in southern Baja, and the other camp calling for landfall farther north near central Baja. The official NHC forecast splits the difference between these two solutions, and landfall could occur anywhere along a long stretch of the Baja coast. At this point, the UKMET model's solution taking Jimena westward out to sea is being discounted, since it is an outlier.

After Jimena makes initial landfall on Baja, it will cross over the Gulf of California and make landfall on Mainland Mexico. Depending upon how up along the coast this second landfall occurs, Arizona may receive moisture from Jimena late this week that will be capable of causing flooding rains.

Invest 94LThe well-organized tropical wave (94L) near 14.5N, 52W, about 500 miles east of the central Lesser Antilles Islands, continues to be a threat to develop into a tropical depression. Visible satellite imagery and this morning's QuikSCAT pass do not show a surface circulation yet, though 94L does have a large envelope of moisture and some modest heavy thunderstorm activity. QuikSCAT noted winds up to 30 mph. Water vapor satellite loops show that 94L has moistened the region surrounding it considerably, and dry air from the Saharan Air Layer is not a major impediment to development. Wind shear is a low 5 - 10 knots, and the ocean temperature are a moderately warm 28°C. Visible satellite loops over the past two hours show low-level spiral bands developing on 94L's northeast side, and I give a 70% chance the Hurricane Hunters will find a tropical depression or tropical storm on Tuesday when they investigate 94L.

The center of 94L probably passed over Buoy 41040, located at 14.5N, 53W over the past hour. Winds blew northeasterly early this morning, then went calm, then shifted to southerly late this morning. The winds were less than 10 knots during the center passage, so the circulation of 94L is not yet well-defined. The pressure fell significantly as 94L moved over the buoy (seen only after one removes the wiggles due to daily atmospheric tide effect present in the tropics). 94L will appear on Martinique radar on Tuesday.

The forecast for 94LShear will remain low, 5 -10 knots, over the next 5 days, SSTs will be warm, in the 28 - 29°C range, and dry air should have only a minor inhibiting effect, so I can't see anything that will prevent 94L from developing into a tropical depression over the next 1 - 2 days. The HWRF model develops 94L into a hurricane 4 days from now, as does the SHIPS intensity model, but other models, such as the GFDL, ECMWF, and GFS, do not develop 94L at all.

Model solutions for the track of 94L are divergent. Water vapor satellite loops show two upper-level lows to the north and northwest of 94L that are pulling the storm to the west-northwest, and 94L's motion is expected to range between the west-northwest and northwest over the next three days. By Tuesday, 94L will slow down from its current 15 mph forward speed to about 10 mph. Most of the models predict that the steering influence of the upper-level lows will pull 94L far enough north that the storm will miss the Lesser Antilles, with a closest approach occurring Wednesday and Thursday. However, the ECMWF and HWRF models have 94L passing within 200 miles of the islands, and the northern Lesser Antilles may experience tropical storm conditions on Thursday.

At the longer ranges, the fate of 94L is highly uncertain. The Canadian model turns 94L to the north near Bermuda, then out to sea, while the NOGAPS model foresees a threat to the U.S. East Coast early next week. Both of these solutions are believable. The Hurricane Hunters are scheduled to make their first flight into 94L on Tuesday afternoon at 2pm EDT.

Elsewhere in the AtlanticThe remains of an old cold front are bringing cloudiness and showers to the northern Gulf of Mexico and waters offshore North and South Carolina. The GFS and NAM models indicate an area of low pressure may develop along this old front near the Florida Panhandle or off the coast of North Carolina by Thursday. However, such a low may be extratropical and not tropical.

Quoting Drakoen:As the system moves to the northwest conditions are forecast to become more favorable for development. Right now it is getting shear. 94L has the classic shear tropical cyclone appearance.

This may be why the HWRF keeps the system weak and then at the end of the run blows it up.

Quoting jrobarch:Can someone tell me why storm systems in the Atlantic recurve to the N and then NE, whereas in the Eastern Pacific they don't seem to? Is it the same effect as the west coast of Africa?

Iam not exactly sure were masters finds 5-10kts on shear during the next to 5 days.Per the 00z ECMWF southwesterly shear should begin to impact 94L soon.This thing should struggle for a while in my view.

Quoting StSimonsIslandGAGuy:Savannahstorm I was thinking the same thing. But then I looked back at Floyd in 1999, forecast to move directly over St Simons as a 120 kt CAt 4. The same thing happened with Frances in 2004, forecast to move directly over St. Simons as a 115 kt Cat4. Every 5 years or so the models bring a Cat 4 to Georgia :) And we have to wait for the forecast track to change. And it always does. Till all we're left with is some lovely surf :)

Yep, Hugo was making a beeline for Savannah when he decided to make a right-hand turn the last day. The models always trend north and right when systems move this way. If the models ever bring something to the Daytona to St. Augustine area, that's when Georgia residents need to worry.

Iam not exactly sure were masters finds 5-10kts on shear during the next to 5 days.Per the 00z ECMWF southwesterly shear should begin to impact 94L soon.This thing should struggle for a while in my view.

This is the 126 hour HWRF forecast. Looks scary, but most agree it may be a little over-done. Most agree, at this time, a CAT 4 may be unlikely. Just showing a graphic, not endorsing it. Got to be careful on the blog.

The way the 2009 Atlantic Hurricane Season has been going we just have to wait and see! Personally, I doubt it will get past a Cat 2!

This is the 126 hour HWRF forecast. Looks scary, but most agree it may be a little over-done. Most agree, at this time, a CAT 4 may be unlikely. Just showing a graphic, not endorsing it. Got to be careful on the blog.